U.S. patent number 4,021,119 [Application Number 05/589,939] was granted by the patent office on 1977-05-03 for position gauge.
This patent grant is currently assigned to Honeywell Inc.. Invention is credited to Norman L. Stauffer.
United States Patent |
4,021,119 |
Stauffer |
May 3, 1977 |
Position gauge
Abstract
An optical gauging apparatus includes structure defining a pair
of light beams. One of the beams comprises a reference beam while
the other is a measuring beam. An object to be gauged is positioned
to partially interrupt the measuring beam. The partially
interrupted measuring beam is compared with the reference beam as
the object to be gauged is run through the gauging process.
Inventors: |
Stauffer; Norman L. (Englewood,
CO) |
Assignee: |
Honeywell Inc. (Minneapolis,
MN)
|
Family
ID: |
24360200 |
Appl.
No.: |
05/589,939 |
Filed: |
June 24, 1975 |
Current U.S.
Class: |
356/638;
250/559.29; 250/559.15; 250/221; 356/429; 250/239 |
Current CPC
Class: |
G01B
11/028 (20130101); G01D 5/34 (20130101) |
Current International
Class: |
G01B
11/02 (20060101); G01D 5/26 (20060101); G01D
5/34 (20060101); G01B 011/10 () |
Field of
Search: |
;356/156,160,167,199,200,256,159 ;250/239,571,578 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Leonard, M. "Digital Noncontact Gages for the Metals Industry",
Proc. 19th Intern. ISA Iron and Steel Instrumentation Symp.,
Pittsburgh, Pa. USA, 17-19, Mar. 1969, pp. 15-25..
|
Primary Examiner: Corbin; John K.
Assistant Examiner: Punter; Wm. H.
Attorney, Agent or Firm: Marhoefer; Laurence J. Burton;
Lockwood D.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An optical gauging means comprising a housing member,
means defining a plurality of compartments within said housing
member,
a light source means mounted in a first one of said
compartments,
means within said housing member for defining a first and a second
effective beam of light from said light source means,
means for directing said first and second effective beams of light
from said first compartment through a second one of said
compartments and into a third one of said compartments,
a first and a second electrically responsive photodetector mounted
within said third compartment, said first photodetector being
positioned to be responsive to said first beam of light and said
second photodetector being positioned to be responsive to said
second beam of light,
means defining a channel across said second compartment and
transverse said first and second light beams, said channel being
adapted to receive an object to be gauged therein in a position to
partiallly interrupt said first light beam, said second light beam
comprising a reference beam,
means differentially responsive to output signals from said first
and second photodetectors as a measure of the gauging of said
object,
said means for defining said first and second light beams including
a lens system for producing light in substantially parallel rays
across said channel,
said lens system forming an image of said light source means within
said third compartment and being characterized by the inclusion of
an aperture plate within said third compartment at the position of
said image of said light source means whereby to effectively
exclude extraneous light.
2. An optical gauging means as set forth in claim 1 wherein said
lens system forms an image of a plane transverse of said channel,
which plane represents the position to be occupied by an object to
be gauged, said last-mentioned image being formed at a position
intermediate said aperture plate and said photodetectors, and
characterized by the inclusion of a further aperture plate at the
position of said last-mentioned image, said further aperture plate
having a first and a second aperture therein corresponding to and
effectively defining said first and second light beam
respectively.
3. An optical gauging means as set forth in claim 2 wherein said
lens system includes a split lens positioned adjacent to said
further aperture plate, one-half of said split lens being
positioned to focus the light passing through one of the apertures
of said further aperture plate onto one of said photodetectors, the
other half of said split lens being positioned to focus the light
passing through the other aperture of said further aperture plate
onto the other of said photodetectors.
4. An optical gauging means as set forth in claim 2 wherein said
first aperture in said further aperture plate is substantially
twice the size of said second aperture in said further aperture
plate whereby to define said first, or measuring, beam as having a
cross-section area substantially twice that of said second, or
reference beam.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gauging means, and more
particularly to apparatus for determining the relative position or
change of position of an object under test.
2. Description of the Prior Art
Heretofore, there have been provided various types of devices for
effecting a gauging of the numerous aspects of measuring and
testing the mechanical properties of an object under test. These
have been in the form of mechanical feeler guages, with
accompanying mechanical metering, for checking run-out, or
eccentricity of a rotatable member. Such feeler gauges have also
been employed to determine dimensional features. Mechanical feelers
of that type have the disadvantage of relative inaccuracies
resulting from relatively low frequency response when used to
determine run-out on a rotating member. For use with a static body,
the mechanical metering means have an inherently limited accuracy
and sensitivity from the mechanical nature of the system. Further,
there are numerous instances wherein it is not desirable to
physically touch the object under test. A contacting gauge under
such conditions would be harmful to the object.
Alternatively, there have been provided, heretofore, optical
sensors as gauges for dimensional determinations. Such optical
gauges are exemplified by several patents issued to Samuel C.
Hurley, Jr., namely, U.S. Pat. Nos. 2,415,174; 2,415,175;
2,415,176; 2,415,177; 2,415,178; 2,415,179. These patents relate to
a means for determining whether or not an object under test matches
prescribed dimensions within established tolerances. Because they
rely on the illumination or obfuscation of one or more pairs of
spaced photodetectors, the relative sensitivity and/or accuracy of
such optical systems are necessarily limited.
In another optical sensing device, a single light source and a
single photodetector are used to detect deformation of a human
eyeball as a means of detecting glaucoma. That device is shown in
U.S. Pat. No. 3,304,769 issued to the present inventor. For precise
measurements, the power supply for the light source as well as the
associated electronic circuitry must be highly regulated in order
to avoid errors due to electrical variations.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
gauging means which obviates the shortcomings of the prior art
devices.
It is another object of the present invention to provide an
improved gauging means, as set forth, which provide very high
accuracy and sensitivity.
It is a further object of the present invention to provide an
improved gauging means as set forth and which features a
non-contacting measurement.
It is yet another object of the present invention to provide an
improved gauging means as set forth which includes
self-compensating stability.
In accomplishing these and other objects, there has been provided,
in accordance with the present invention, an optical gauging means
which includes a single radiation source, and means for deriving a
pair of beams from that single source. One of the beams constitutes
a reference beam; the other is a measuring beam. The two beams are
so directed that one may be partially interrupted by an object to
be gauged. The beams are thereafter directed to impinge on a pair
of photodetectors, the outputs of which are compared to produce a
difference signal representative of the gauging of the object.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention may be had from the
following detailed description when read in connection with the
accompanying drawings in which:
FIG. 1 is a cross-sectional view of a schematic representation of a
structure embodying the present invention;
FIG. 1a is a plain view of an alternate arrangement of a portion of
the structure shown in FIG. 1;
FIGS. 2 and 3 are views of a contact feeler for use with the
structure shown in FIG. 1; and
FIG. 4 is a schematic diagram of a circuit suitable for use in
carrying out the present invention.
DETAILED DESCRIPTION
Referring, now, to FIG. 1 in more detail, there is shown a housing
member 2. A source of radiation represented by a lamp 4 is mounted
in a first compartment 6 in the housing 2. An opening 8 through one
of the walls defining the first compartment 6 allows radiation from
the source member 4 to pass into a second compartment 8 of the
housing 2.
In the second compartment 10, there is positioned a first
condensing lens 12, a first prism 14, a second prism 16 and a
second condensing lens 18. The positional relationship of the first
condensing lens and the lamp 4 is such that the radiation source is
effectively at the focus of the lens 12 whereby the radiation from
the source 4 is formed into parallel rays. The first prism 14 is
positioned to change the direction of those parallel rays by
90.degree.. A transverse channel 20 is formed across the second
compartment 10 to accommodate an object 22 to be gauged. Each of
the facing walls of the channel 20 has a window 24, 26,
respectively, therein. The parallel rays are directed by the first
prism 14 through the first window 24 toward the second window 26.
The second prism 16 is positioned behind the second window 26 to
receive the parallel rays and again change their direction by
90.degree..
The redirected rays from the second prism 16 are passed through the
second condensing lens 18 whereby the radiation is reformed into a
converging bundle of rays. The converging bundle of rays is
directed through an opening 28 into a third compartment 30. A first
aperture plate 32 has an opening or pupil 54 therein. The first
aperture plate is located within the third compartment at a
position which coincides with the image of the radiation source 4
formed by the lenses 12 and 18. A second aperture plate 36 has a
pair of openings or pupils 38. The second aperture plate 36 is
mounted within the third compartment 30 at a position which
coincides with the image plane of an object 22 placed in the
channel 20.
A split condensing lens 40 is mounted behind and adjacent the
second aperture plate 36. The radiation passing through the two
pupils 38 of the plate 36 is focused separately, due to a slight
displacement of the two halves of the split lens 40, on two
electrically responsive photosensitive radiation detectors 42 and
44, respectively.
In operation, the radiation source 4 is energized from a reasonably
regulated power supply (not shown). The radiation is illustrated as
comprised of two beams. The two beams are effectively established
by the two pupils or apertures 38 of the second aperture plate 36.
Since both beams are derived from the same source 4, one of the
beams may be used as a reference beam while the other beam
constitutes the measuring beam.
The location of the first aperture plate 32 at the plane of the
image of the radiation source 4 restricts the light impinging on
the detectors 42 and 44 to only the light coming from that source.
Ambient light, even light which is reflected at grazing incidence
off surfaces of the object 22, is eliminated.
In a preferred embodiment, the cross-sectional area of the
reference beam is substantially one-half the cross-sectional area
of the measuring beam, as shown in FIG. 1a. Thus, an initial or
reference position of the object relative to the gauging means is
established when the two beams are effectively balanced.
The two beams are, as has been set forth, arranged to impinge on
the separate photodetectors 42 and 44. Through electronic means, to
be hereinafter shown, the output signals for the two photodetectors
may be balanced to constitute the reference condition. If the
object being gauged is to be gauged for eccentricity or run-out,
the reference condition may be established with the object in a
stationary position partly intercepting the measuring beam. Then
when the object is rotated, the change in the status of balance
between the two beams is a function of the eccentricity or run-out
of the object under test. Since the two beams are derived from the
same source, minor variations in the energization of that source
does not introduce disturbing inaccuracies in the resulting
measurement; the same variations occur in both beams and the
measurement is a function of the differential between them.
In an apparatus constructed in accordance with the present
invention, with beam thickness of 0.020 inch, a resolution of one
microinch was obtained with a response time of less than one
millisecond.
It will be appreciated that, in addition to the measurement of
run-out, the apparatus may also be used to gauge stationary objects
as well. Further, the device may be used as a very precise
thickness gauge for web material passing over a predetermined
reference surface.
While the gauging means of the present invention is uniquely
adapted to providing a highly sensitive, accurate, stable and
reliable measurement relative to an object, without physically
touching that object, there are instances wherein there is a need
for gauging an object on a physical contact basis. For example, it
may be desired to gauge the surface of a flat sheet member, or an
object which is too large to fit within the channel 20 of the
structure shown in FIG. 1. The gauge of the present invention may
still be used to provide a highly accurate, stable contact gauging.
The structure shown in FIGS. 2 and 3 includes an attachment for
converting the optical gauge to a contact gauge. To that end, there
is shown the gauge housing 2 with the elements therein as shown in
FIG. 1. To the top of the housing 2 there is secured a contact
feeler 46. The feeler 46 is made of a suitable spring material
secured at one end, as by a pair of screws 48, to the edge of the
housing 2. The other end of the feeler 46 is cantilevered over the
channel 20, then bent at substantially a right angle away from the
channel 20 and terminating in a contact point 50. The contact point
50 may be in the form of a ball. A vane 52 is attached to the
feeler member 46 and is positioned to extend into the channel 20.
The structure is so arranged that in an unloaded or normal
condition, the quiescent position of the spring cantilever holds
the vane 52 just out of the path of the measuring beam of the
optical measuring system. When the apparatus is put into operation,
the ball contact point 50 is placed in engagement with the surface
to be gauged. The structure is then positionally adjusted until the
vane 20 interrupts one-half of the measuring beam and the resultant
signals from the two photodetectors balance. When the object or
surface being gauged is then moved relative to the contact point
50, any change in dimension will be reflected by an unbalance of
the resulting electrical signals, with substantially the same
degree of sensitivity, accuracy and stability as the non-contacting
mode.
An electronic circuit suitable for use in connection with the
present invention is schematically shown in FIG. 4. The
photodetector 42 responsive to the measuring beam is coupled to the
input of an amplifier 54 while the reference photodetector 44 is
coupled to the input of a similar amplifier 56. A variable feedback
resistor 58 connected across the amplifier 56 permits the output of
that amplifier to be adjusted to effect an initial "zero" condition
for the measuring system. The output signals from the amplifiers 54
and 56 are applied, respectively, to the input terminals of a
differential amplifier 60.
The output of the differential amplifier 60 is applied, first, to
the input of a first range control amplifier 62, the output of
which is applied to the input of a meter driver amplifier 64. A
suitable meter 66, preferably a center-zero meter, is connected to
respond to the output of the amplifier 64. Between the output of
the differential amplifier 60 and the input of the first range
control amplifier there is connected a variable resistor 68 which
provides a calibration control for the meter 66. A bank of
resistors 70 is arranged for selective connection in feedback
relation with respect to the first range control amplifier whereby
to effect changes in the sensitivity range of the measurement
indicated on the meter 66.
The output of the range control amplifier 62 is also arranged for
application to other utilization apparatus 72 which may, for
example, be an oscilloscope, an oscillograph or a signal
analyzer.
The output of the differential amplifier 60 is also applied to the
input of a second range control amplifier 74 through a second
calibration resistor 76. Again, an impedance bank 78 is arranged
for selective connection in feedback relation with respect to the
second range control amplifier whereby to effect changes in the
operating range of the instrument controlled thereby. The output of
the second range control amplifier is applied to the input of a
pair of peak detectors 80 and 82, one of which detects and holds a
positive peak while the other detects and holds a negative peak.
The output of these two peak detectors is applied, respectively, to
the input terminal of a differential amplifier 84. The output of
the differential amplifier 84 is applied to the input of a digital
voltmeter 86. The indication displayed by the digital voltmeter 86
will, therefore, be representative of the total (peak to peak)
run-out, eccentricity or deviation of the dimensions of the object
being gauged.
In order to determine that the range selection effected by
selection of the individual feedback resistors from the bank 70 is
an appropriate range, there is provided a signal limit alarm means.
That limit alarm means comprises a positive signal limit detector
88 and a negative signal limit detector 90. An alarm device 92,
which may be in the form of a light emitting diode, is connected to
respond to an output signal from the positive signal limit detector
88. A similar alarm device 94 is connected to respond to an output
signal from the negative limit detector 90. If a relatively small
range selection has been effected by the range control amplifier, a
short but large signal peak would not be properly indicated on the
meter 66. Such a peak would cause one or the other (or both of the
alarms 92 and 94) to be actuated, alerting the operator to change
the range.
Thus, there has been provided, in accordance with the present
invention, an improved gauging means for effecting a highly
accurate and sensitive measurement of dimensional characteristics
of an object to be gauged, which features the effecting of the
measurement without the necessity of physically touching the object
and which features a selfcompensating stability.
* * * * *